Cold cathode fluorescent lamps (CCFLs) are used as inexpensive light units in electrical devices. Both liquid crystal display (LCD) monitors (e.g., single-lamp LCD monitors, and multiple-lamp LCD monitors) and liquid crystal display televisions (LCD TV) can use CCFLs as a backlight because the relatively high illumination efficiency of the CCFL. A CCFL inverter is a device for providing a driving power to one or more CCFLs. However, the drive power is of high voltage. At the moment of a start-up of the CCFL, the driving power can raise to over 1800 volt. As a result, a crisis situation (e.g., striking fire) may occur and it can be dangerous without sensing the drive power.
As such, an over-voltage protection is necessary to help avoid the crisis situation. Conventionally, a sensing voltage can be monitored by the CCFL inverter. The sensing voltage is proportional to the driving power. The CCFL inverter senses the sensing voltage instead of the driving power. A high-voltage capacitance divider or a high-voltage resistance divider is usually used to convert the drive power to a sensing voltage that is within a safe range of the CCFL inverter so that the CCFL inverter can sense the sensing voltage safely. However, the high-voltage capacitance divider and the high-voltage resistance divider can be costly. Furthermore, the high-voltage capacitance divider and the high-voltage resistance divider respectively include a high-voltage capacitor and a high-voltage resistor which can cause high temperature. In addition, the high-voltage capacitor usually has a high capacitance which may cause high leakage current, thereby resulting in current unbalance. As a result, the CCFL inverter may not function stably and the lifetime of the CCFL inverter may be shortened.